NEC IR Protocol remote decoder, help me before I kill myself!

[Bruce]

There are much better/faster ways to do this, but this should get you started with something that's fairly easy to understand.

Assuming you have an NEC transmitter that outputs something like the top portion of the graphic below;

This should return similar results to what's shown in the serial terminal window just above.

#CONFIG
  __config _XT_OSC & _WDT_ON & _MCLRE_OFF & _LVP_OFF & _CP_OFF
#ENDCONFIG
 
DEFINE OSC 4
 
Leader VAR WORD     ' will be up to 900 for a 9mS leader pulse
BtnVal VAR BYTE[32] ' holds 32 pulse results
DByte1 VAR BYTE     ' address byte
DByte2 VAR BYTE     ' inverse of address byte
DByte3 VAR BYTE     ' command byte
DByte4 VAR BYTE     ' inverse of command byte
X      VAR BYTE     ' loop count
 
Main: 
  PULSIN PORTB.0,0,Leader  ' leader pulse is ~9mS low-going
  IF Leader < 850 THEN Main
 
  FOR X = 0 TO 31          ' grab 32 incoming pulses
      PULSIN PORTB.0,1,BtnVal(X) ' now measuring high-going pulse widths
  NEXT X
 
  ' now we'll decode 4 bytes from 32 pulses
  FOR X = 0 TO 7               ' sort 1st 8 pulses
      IF BtnVal[X] > 150 THEN  ' > 150 x 10uS = > 1.5mS pulse period
         DByte1.0[X]=1
      ELSE
         DByte1.0[X]=0
      ENDIF
  NEXT X
 
  FOR X = 8 TO 15              ' sort 2nd 8 pulses, etc....
      IF BtnVal[X] > 150 THEN
         DByte2.0[X-8]=1
      ELSE
         DByte2.0[X-8]=0
      ENDIF
  NEXT X
 
  FOR X = 16 TO 23
      IF BtnVal[X] > 150 THEN
         DByte3.0[X-16]=1
      ELSE
         DByte3.0[X-16]=0
      ENDIF
  NEXT X
 
  FOR X = 24 TO 31
      IF BtnVal[X] > 150 THEN
         DByte4.0[X-24]=1
      ELSE
         DByte4.0[X-24]=0
      ENDIF
  NEXT X
 
  HSEROUT [BIN8 DByte1,13,10,BIN8 DByte2," Address",13,10,13,10]
  HSEROUT [BIN8 DByte3,13,10,BIN8 DByte4," Command",13,10,13,10]
  PAUSE 1000
  GOTO Main